Just a word of warning before you go and automate using rbl's and the such. In theory they are great, however, they do have their flaws. I have seen mail servers get black listed due to their configurations that made them look like an open relay when in fact they were not. With the RBL's, they just run a quick scan to see if a server will accept anonymous connections. They do not check to see what happens with that connection after it is received (if it is thrown out or not). This may cause you to miss some important emails from people that are incorrectly listed by rbl's. I would suggest filtering purely on content (such as see britney..., get your degree... and the such.) rather than a black hole which can incorrectly filter out email that does not meet their specifications.

"The social dynamics of the net are a direct consequence of the fact that nobody has yet developed a Remote Strangulation Protocol." -- Larry Wall